Thursday, October 05, 2006

How to rename an XML Node in C#


This was driving me crazy - here's an easy cut and paste solution to not being able to use the DOM to rename a node for lazy developers like me:

public static XmlNode RenameNode (XmlNode node, string namespaceURI,string qualifiedName)
{
if (node.NodeType == XmlNodeType.Element)
{
XmlElement oldElement = (XmlElement) node;
XmlElement newElement =
node.OwnerDocument.CreateElement(qualifiedName, namespaceURI);

while (oldElement.HasAttributes)
{
newElement.SetAttributeNode(oldElement.RemoveAttributeNode(oldElement.Attributes[0]));
}

while (oldElement.HasChildNodes)
{
newElement.AppendChild(oldElement.FirstChild);
}

if (oldElement.ParentNode != null)
{
oldElement.ParentNode.ReplaceChild(newElement, oldElement);
}

return newElement;
}
else
{
return null;
}
}

Ahh. That's better :)

7 comments:

  1. Just saw your post too late and developed my own solution!

    The following works given that you are iterating over some of the nodes in the document, and have stored them in an ArrayList of XmlNode's called 'oldNodes'. I had to use indexed access to the ArrayList rather than iteration (with a foreach), as the latter had 'unexpected' results!


    for(int i=0; i < oldNodes.Count; i++)
    {
    XmlDocumentFragment f = doc.CreateDocumentFragment();
    XmlNode old = oldNodes[i] as XmlNode;
    f.InnerXml = old.OuterXml.Replace(old.Name, newName);
    old.ParentNode.ReplaceChild(f.ChildNodes[0], old);
    }

    Eoghan http://eoghan.qatano.org/

    ReplyDelete
  2. Anonymous7:12 am

    Great piece of reusable code. Saved me some time. Thanks!!

    ReplyDelete
  3. Stiefel12:34 am

    Sorry Eoghan, but i think your code fails if the tag-name is used in some child node again -> in this case all tags are renamed ..

    ReplyDelete
  4. Anonymous10:14 am

    Just noticed that you posted this in 2006...well, it still works great in 2011! Thanks!

    ReplyDelete
  5. Anonymous11:03 pm

    public static XmlNode RenameNode (XmlNode node, string namespaceURI,string qualifiedName)
    {
    if (node.NodeType == XmlNodeType.Element)
    {
    XmlElement oldElement = (XmlElement) node;
    XmlElement newElement =
    node.OwnerDocument.CreateElement(qualifiedName, namespaceURI);

    while (oldElement.HasAttributes)
    {
    newElement.SetAttributeNode(oldElement.RemoveAttributeNode(oldElement.Attributes[0]));
    }

    while (oldElement.HasChildNodes)
    {
    newElement.AppendChild(oldElement.FirstChild);
    }

    if (oldElement.ParentNode != null)
    {
    oldElement.ParentNode.ReplaceChild(newElement, oldElement);
    }

    return newElement;
    }
    else
    {
    return null;
    }
    }

    ReplyDelete
  6. 3 issues:

    1. Signature should be changed to
    public static XmlNode RenameNode (this XmlElement node, string namespaceURI,string qualifiedName)

    this allow 1, remove the unncessery check, and use the code as extention method for XmlElements

    myElement.RenameNode("newName");


    2. there is a problem with references kept to the old node, which are NOT updated


    3. this is a very lengthy operation which traverse a lot of items (possibly) so use it only when REAALLY necessery.


    Other then that, Kudos.
    nice work.

    ReplyDelete
  7. Anonymous4:04 pm

    What if the oldElement has no parent node, i.e renaming an XmlElement directly under the XmlDocument as DocumentElement?

    ReplyDelete